The use of tufting machines to create tufted articles, for example tufted carpet, is well known in the art. Conventional tufting machines use a reciprocating needle bar carrying a plurality of aligned needles of a predetermined gauge, the needles being constructed and arranged to reciprocably penetrate a backing material passing beneath the needle bar and over a bedrail. As the needles penetrate the backing materials they each carry a separate yarn which yarn is caught either by a looper to create a looped pile article, or by a hook moving, in timed relationship with a knife to create a loop of tufted material which is then cut to create a cut pile article. It is by these well known processes, that loop pile and cut pile carpeting is made.
In order to create patterned tufted articles, the amount of yarn fed to certain needles of the tufting machine is varied so that either high or low piles, respectively, are formed in a patterned series defined in the face of the carpet in the desired shape, design, and/or configuration. Although other methods and devices exist for creating patterns in carpet, to create the pattern within a tufted article, by this method it is necessary therefore to control the amount of yarn fed to the individual tufting machine needles in order to produce the desired pattern. This has been accomplished by using a pattern yarn feed drive assembly, also known as a scroll attachment, which is constructed to control the feed rate of the yarns to the needles of the tufting machine.
One example of such a pattern yarn drive assembly is the YARNTRONICS pattern assembly manufactured by Card-Monroe Corp. of Chattanooga, Tenn., disclosed in U.S. Pat. No. 4,688,497 (the "'497 patent"). The '497 patent discloses a tufting machine a yarn feed mechanism having a plurality of yarn feed rollers, known as controls, disposed in spaced series and operably engaged with either one of a high speed or a low speed drive shaft, respectively, each of the drive shafts being driven in synchronization with the rotation of the tufting machine main drive shaft, and thus in synchronization with the reciprocation of the needles through the backing material. As the yarn is fed to the needles of the tufting machine, predetermined yarn feed rollers are rotated at either a relatively high rate of speed or a relatively low rate of speed with respect to one another such that a sufficient amount of yarn is supplied to associated needles to form either a full height or "high" pile, or a looped "low" pile. If the yarn is fed more slowly to the needles, a low pile is created by "back-robbing" the yarn, in which the yarn is drawn back toward the backing material on the upstitch portion of the tufting cycle to tuft a low pile. In some instances certain yarns may be drawn back snugly against the backing material so that the yarn is masked by the high piles of the carpet until such time as that particular yarn color is desired in the pattern being created in the face of the tufted article.
As known to those skilled in the art, each separate needle which receives a yarn from a given feed roller, or control, will tend to produce a pile having the same relative height as that of the other needles receiving yarn from the same feed roller. To produce patterns, the needles are provided with yarns in a recurring series of a predetermined number of yarns, known as a repeat. The repeats are duplicated in series across the width of the tufting machine. For example, assuming a tufting machine is provided with 72 control pairs, or controls which may comprise a low speed and a high speed yarn drive roller supported on a frame extending the width of the tufting machine, and the gauge or distance between each needle with respect to the adjacent needles in series is one-quarter of an inch, then one spaced series of 72 needles will extend approximately 18 inches, or approximately 45 cm in width. This spaced series of needles will need to be "repeated", therefore, forming a series of "repeats" 18 inches, or approximately 45 cm, wide across the desired width of the tufted article. Thus, if it is desired to produce a tufted article of approximately 13 & 1/2 feet, or approximately 4 meters, in width, nine such repeats of 72 needles per repeat are required. Accordingly, each of yarn feed drive rollers would have nine separate tufting yarns passed thereover with each one of those yarns being passed on to the corresponding needles of each repeat, for example the first needle in the repeat. Thereafter, the next control pair of yarn feed drive rollers would have nine yarns passed thereover and to the second needle of each repeat, and so on. The repeat width is determined by multiplying the number of controls by the gauge of the needles. The repeat width is then multiplied by the appropriate number to arrive at the appropriate or desired width of the tufted article to be produced.
As a practical limitation, the number of controls provided as a part of the pattern yarn drive assembly is oftentimes determined by the physical limitations of providing sufficient numbers of controls as a part of the pattern yarn drive assembly. As discussed above, if a fourth guage tufting machine is provided with an 18-inch repeat width, 72 control pairs of yarn feed drive rollers are provided. Although it is desirable to feed each needle with yarn separately of the others, it is difficult to provide a separate control pair for each needle as the total number of needles for nine repeats of 72 needles comprising the width of the tufted article equals 648 needles, which would require 648 control pairs if a control pair were to be provided for each needle and yarn. Accordingly, the necessity of using "repeats" to tuft patterned tufted articles has arisen.
Where a tufting machine constructed to tuft patterned articles is provided with a pattern yarn drive assembly, a means must be provided for passing the yarns from each control to the appropriate needles of the repeats across the width of the tufting machine. This can be accomplished by using a tube bank as disclosed in U.S. Pat. No. 2,862,465 to Card (the '465 patent"). In the '465 patent, a tube bank was created from a plurality of guide tubes, one guide tube being provided for each yarn passing to each respective one of the needles of the tufting machine. Thus, for a machine having 72 control pairs of drive rollers feeding 72 yarns to nine different repeats, the tube bank of the '465 patent would be comprised of 648 yarn tubes extending from a point adjacent the respective controls to a point at or close to the appropriate needle mounted on the needle bar of the tufting machine. By fashioning the tube bank in this manner, the appropriate yarns would be guided to the appropriate needles without allowing the yarns to become tangled which would otherwise necessitate machine shut down in order to re-thread the machine.
One problem that has arisen with the use of tube banks, however, is that typically certain of the tubes will be longer than others for corresponding yarns/needles within a repeat as the repeats extend across the width of the tufting machine. For example, and as illustrated in FIG. 1C, the yarn extending from the first control of a pattern yarn drive assembly to the first needle of each of the nine repeats will have nine different lengths, with the length of the yarn closest to repeats 1, 2, and 3 being less than the length of the yarn extending from the first control to the first needle of repeats 7, 8, and 9, respectively. As a result, given the inherent elasticity of the yarn or yarns being used to create the tufted article, it sometimes occurs that when yarn is being back-robbed or fed more slowly to tuft a "low" pile, there tends to be a delay in the time between the slowing of the yarn respective control to the time that the yarn is actually slowed at the appropriate needle of the tufting machine, such that two or three stitches may pass before the yarn is withdrawn, or back-robbed, toward the backing material to create the a low or buried tuft. The reverse effect can also happen such that when the yarn feed rate is increased, for example when changing from a low pile to a high pile, it may take two or three stitches before the yarn is at its full pile height. In both instances, this can result in a lack of pattern definition in the face of the carpet, particularly along the lines adjoining adjacent repeats across the width of the tufted article. This effect is typically more pronounced at the outer margins of the tufted article, and is known generally as pattern fade or tube bank streaks. This effect is illustrated schematically in FIG. 1E, which illustrates the pattern yarn drive assembly of FIG. 1C in which the yarns are fed to nine repeats spaced across the width of the machine, and in which the relative pile height is illustrated, not to scale, below the respective repeats to illustrate how problems in pattern definition or "chop" can occur between repeats across the width of the carpet.
In the effort to combat this loss of pattern definition in the face of the tufted articles include the use of scrambled tube banks with a pair of opposed and counter-rotating puller rolls. A scrambled tube bank is illustrated schematically in FIG. 2A, in which the control pairs, i.e. the high speed and low speed drive rollers, respectively, of the pattern yarn drive assembly are positioned out of a strict ascending or numbered order, as shown in FIG. 1A, for example, across the width of the pattern yarn drive assembly for the purpose of trying to "blend" or more uniformly guide the yarns being used in each of the repeats, nine such repeats in FIGS. 1C and 1E for example, such that a more uniform or blended appearance occurs, which is illustrated schematically in FIG. 2C. However, this may still result in some pattern definition loss in the face of the carpet, which is generally shifted more toward the center of each repeat and away from the adjoining lines of each repeat such that a distinct pattern fade or chop at the adjoining side edges of each repeat is minimized to provide a more uniform finished look across the face of the tufted article. As with the tube bank of the '465 patent to Card, the use of scrambled tube banks has become commonplace in the tufting industry.
However, even with the use of scrambled tube banks the problem persists that a single control is provided for a yarn, or the yarns being fed to respective needles of each repeat across the width of the tufting machine, such that some of the needles within the repeat patterns will ultimately be subject to the problems of yarn elasticity and yarn feed lag during the tufting of the article, with resulting pattern definition loss in the face of the tufted article. What is needed, therefore, is an improved tufting machine pattern yarn feed and distribution device constructed for the purpose of minimizing the lengths of the yarns from the respective control pairs to the needles of the repeats of the tufting machine such that the problems of yarn elasticity and feed lag are minimized. Moreover, there is a need for such an improved tufting machine pattern yarn feed and distribution device which may use existing components to the greatest extent possible in order to minimize manufacturing and operating costs of the device.